I can tell you this: Your customer's info is probably right. I just bought a new 12c+, and a 15C LE. They are supposed to have the same hardware, and, hence the same keyboard feel. Not so, by a long shot. The 15c LE keyboard is much harder and more precise. The 12c+ keyboard is much softer (even though not mushy). Additionally, is has receding keys and a defective Enter key (I'm now having the calculator replaced). The key print is exactly the same you have on the picture (the "new", "sub-par", one).

Different factory? Different assembly line? Different dome materials? I don't know. But I know this: different ball game.

I believe that the first 3 characters of the serial number denote the factory of manufacture (country also, but that is China in all cases.) So the calculators pictured were made in different factories, 4CY vs. CNA. My 15c LE was made in the CNA factory. Where was your 12c+ made?

Yes, 4CY is a different factory. I do not work for HP or either of these companies, so I am not 100% sure, but I believe that 4CY == Inventec Appliance, and CNA == Kinpo Electronics.

We know HP uses both of these manufacturers (They've admitted to using Kinpo, and some of the PDFs in the 20b SDK had engineering drawings by Inventec).

My reasoning for believing this mapping of serial number to manufacturer is as follows:

We know that Kinpo made the HP-35s, and the 35S has a "Regulatory Model Number" molded into the back that reads HSTNJ-KN01, and a serial number beginning with CNA.

My 30b has a serial number beginning with 4CY and a "Regulatory Model Number" of HSTNJ-IN07. My 12c+ looks like the 'unexpected' one and has a 4CY serial number, regulatory model number HSTNJ-IN04. Also, the 30b and 12c+ serial number stickers are the same color and same font.

My 15C LE has a CNA serial number and model number HSTNJ-KN13. Its' serial number sticker doesn't match the 30b or 12c+ ones.

And sure enough, if you look at the picture of the backs of the two 12c+es, you'll notice "HSTNJ-IN04" underneath the multilingual "Product of China" on the 4CY one, and "HSTNJ-KN05" underneath "Product of China" on the CNA one.

My "sub-par" 12c+ (I love the use of "sub-par", when referring to a less than good financial calculator ;-) ) is also a 4CY. Hence, and trying to apply a little bit of abductive reasoning (even though three or four cases are not a sufficient basis for statistical inference), it would seem that:

1. CNA is producing keyboards which are hard and precise.

2. 4CY produces keyboards with lower overall quality.

3. Both 4CY and CNA produce keyboards with ocasional bad keys (eventually at a more than acceptable rate - see the 15c LEs).